Precorneal tear film

The precorneal tear film is a thin fluid layer that covers the anterior surface of the cornea. It plays an essential role in maintaining ocular health by providing lubrication, protecting against environmental insults, supporting optical clarity, supplying nutrients to avascular tissues like the cornea, and serving as part of the immune defense system. The classic model describes three distinct layers: - Inner mucus/mucin layer: Adheres tightly to epithelial cells of the cornea/conjunctiva; helps spread tears evenly across the eye's surface. - Middle aqueous layer: Composed mainly of water with dissolved nutrients and ions; constitutes most of the volume. - Outer lipid layer: Secreted by meibomian glands; reduces evaporation from underlying layers. Recent research suggests these layers are not strictly separated but intermix without clear boundaries. The total thickness is approximately 6–7 μm. Dysfunction or instability in any component can lead to conditions such as dry eye disease. The precorneal tear film is not considered a therapeutic "target" in terms commonly used for drug development—such as receptors or enzymes—but rather an anatomical/physiological structure maintained by various secretions from glands around the eye. Therefore, listing it among druggable targets would be incorrect.

Other names

Tear filmOcular tear filmPrecorneal tear layer

Not applicable as it is not a molecular target; treatments act by supplementing or stabilizing its layers rather than binding/interacting with it at a molecular level.